Too rich on my DCOEs
Discussion
I don't think my budget will run to a new pair of 40s and I'm a long way away from giving up on the ones I have. I hate them and love them all at the same time!
Andrew, you are dead right that ignition timing plays a huge role in how well these carbs work and for my 234 cam I'm running 14 degrees advance at 1000 RPM. This should be about right for this cam and I can't hear any pinking but I'm a tad mutton (deaf to our continental friends) and most of the noise I do hear is induction hiss and the exhaust bark when I I boot it. I'm very aware that you can easily wreck an engine through running too lean or too much advance but a combination of test runs and plug inspections should get me very close.
I did make a little bit of progress yesterday in the fact that I found that the new "leaner" idle jets (F845) that I fitted in an attempt to lean the idle were much less likely to do the job than the F945s I removed! The F9s should be richer but when I closely inspected it was obvious that the air holes had been drilled out. I've run a 1.5mm drill into the airhole just to ream up the hole and get them all the same size and in effect they are now f545s. I also found out that the hotter plugs I thought I had fitted, were in fact cooler. As Richard has said, a slightly warmer plug might overcome the low speed fouling. Being a knob, I thought that the larger plug number equated to a warmer plug and it is the opposite! So, have fitted the BP6s, balanced the air flows and tickover and I will be off for a blat to see how she runs.
Andrew, you are dead right that ignition timing plays a huge role in how well these carbs work and for my 234 cam I'm running 14 degrees advance at 1000 RPM. This should be about right for this cam and I can't hear any pinking but I'm a tad mutton (deaf to our continental friends) and most of the noise I do hear is induction hiss and the exhaust bark when I I boot it. I'm very aware that you can easily wreck an engine through running too lean or too much advance but a combination of test runs and plug inspections should get me very close.
I did make a little bit of progress yesterday in the fact that I found that the new "leaner" idle jets (F845) that I fitted in an attempt to lean the idle were much less likely to do the job than the F945s I removed! The F9s should be richer but when I closely inspected it was obvious that the air holes had been drilled out. I've run a 1.5mm drill into the airhole just to ream up the hole and get them all the same size and in effect they are now f545s. I also found out that the hotter plugs I thought I had fitted, were in fact cooler. As Richard has said, a slightly warmer plug might overcome the low speed fouling. Being a knob, I thought that the larger plug number equated to a warmer plug and it is the opposite! So, have fitted the BP6s, balanced the air flows and tickover and I will be off for a blat to see how she runs.
Cracked it. Smooth tick-over, flat spot-free and plugs the colour of rich-tea biscuits! I'm glad I have stuck with the 30mm chokes because the car pulls so well, even from very low revs and under load - it absolutely flies uphill and a few times today I had to remind myself that I'm already carrying points on my licence! It still occasionally pops on the over-run but overall a massive improvement right through the range. Obviously the warmer plugs have helped when the car is just ticking over in combination with slightly more airy idle jets and the F11 emulsion tubes.
A big thank you to all for the helpful advice.
A big thank you to all for the helpful advice.
tomtrout said:
Cracked it. Smooth tick-over, flat spot-free and plugs the colour of rich-tea biscuits! I'm glad I have stuck with the 30mm chokes because the car pulls so well, even from very low revs and under load - it absolutely flies uphill and a few times today I had to remind myself that I'm already carrying points on my licence! It still occasionally pops on the over-run but overall a massive improvement right through the range. Obviously the warmer plugs have helped when the car is just ticking over in combination with slightly more airy idle jets and the F11 emulsion tubes.
A big thank you to all for the helpful advice.
That's Fantastic Andy I was getting worried as after all your hard work its time you where out enjoying the fruits of your labour looking forward to seeing the rear end as it pulls away from me on the road FantasticA big thank you to all for the helpful advice.
Andrew
When I first ran a car with DCOEs the local tuning shop would exchange jets and tubes for way less than the new cost which was really handy.
Unfortunately this had to stop because customers would drill jets then exchange them which really buggered things up, especially if you unwittingly combined drilled jets with normal ones.
You could of course check the jet sizes with a gauge but people were drilling emulsion tubes as well.
Unfortunately this had to stop because customers would drill jets then exchange them which really buggered things up, especially if you unwittingly combined drilled jets with normal ones.
You could of course check the jet sizes with a gauge but people were drilling emulsion tubes as well.
)There's a purity factor to the DCOE series, that can't be undersold, but I had nice copies, on my 2500 straight six.
I'm not referring to the Spanish made Webers. What I'd lucked into were SK (Japan) copies of Weber DCOEs, with externally adjustable float level, externally readable float level, and improved progression circuits, which extend into the main circuit a little bit more. To those of you still looking for a DCOE type carburetor, I would highly recommend these. All internal components are Weber DCOE.
Best,
B.
I'm not referring to the Spanish made Webers. What I'd lucked into were SK (Japan) copies of Weber DCOEs, with externally adjustable float level, externally readable float level, and improved progression circuits, which extend into the main circuit a little bit more. To those of you still looking for a DCOE type carburetor, I would highly recommend these. All internal components are Weber DCOE.
Best,
B.
My understanding is that you can tune webers to do what you want. Bigger chokes and jets for more power. Go smaller for better mpg. Keeping air/fuel right is the key to tuning.
My Xflow with 234 cam, flowed head, exhaust etc: twin 45's Italian DCOE 13's
Choke 38
Main. 155, Airs. 165
Idle. 60f8
Gives Mondeo man an open jaw to see a 42 year old sprinting.
Of course it likes a good drink. Who does'nt. !!! :-)
My Xflow with 234 cam, flowed head, exhaust etc: twin 45's Italian DCOE 13's
Choke 38
Main. 155, Airs. 165
Idle. 60f8
Gives Mondeo man an open jaw to see a 42 year old sprinting.
Of course it likes a good drink. Who does'nt. !!! :-)
Slow M said:
There's a purity factor to the DCOE series, that can't be undersold, but I had nice copies, on my 2500 straight six.
I'm not referring to the Spanish made Webers. What I'd lucked into were SK (Japan) copies of Weber DCOEs, with externally adjustable float level, externally readable float level, and improved progression circuits, which extend into the main circuit a little bit more. To those of you still looking for a DCOE type carburetor, I would highly recommend these. All internal components are Weber DCOE.
Best,
B.
Sorry for going a little off topic again. I've not heard of SK before. Do they make SU copies too? Externally adjustable and readable floats would be a godsend.I'm not referring to the Spanish made Webers. What I'd lucked into were SK (Japan) copies of Weber DCOEs, with externally adjustable float level, externally readable float level, and improved progression circuits, which extend into the main circuit a little bit more. To those of you still looking for a DCOE type carburetor, I would highly recommend these. All internal components are Weber DCOE.
Best,
B.
Chris
Mr Tiger said:
Sorry for going a little off topic again. I've not heard of SK before. Do they make SU copies too? Externally adjustable and readable floats would be a godsend.
Chris
SK only made DCOE copies, to the best of my knowledge. Chris
If you are after Japanese copies of SUs, look for Hitachi carburetors.
Best,
B.
tomtrout said:
I'm running a pair of sidedraft webers with my 1700 x-flow and I'm strugging to lean off my idle circuit. Before everybody tells me to whizz off and find a rolling road specialist, I have already invested in a session and although some progress was made I'm still running too rich. The car is brilliant if I start of with fresh plugs, fire her up and steam off over the horizon. A plug check suggests the car is running rich - not unusual i guess when running these carbs but the trouble starts if I let the car idle for any length of time because the plugs will foul up and the car misfires when I pull away.
At the moment the carbs are fitted with 30mm chokes which from what I can gather are great for increasing air flow through the carbs at low revs but might be one reason why I'm having trouble leaning off the mixture. I don't really want everything to come in over 4000rpm so I don't necessarily want massive air flow from big chokes but I wonder if I went up a size if would help me rain in the fuel ratio mix at low and medium revs. Also any thoughts on emulsion tubes. F16 is what I have but there seems to be a school of thought that F11 tubes perform well when mated to a cooking crossflow?
Just for info I'm currently running 30 chokes, 120 mains, 195 air correctors, 45F8 idles jets. I know this is a massive can of worms but it's all part of the fun! Any thoughts/advice from any weber gurus out there?
Try some NGK BPR7E1X Plugs.At the moment the carbs are fitted with 30mm chokes which from what I can gather are great for increasing air flow through the carbs at low revs but might be one reason why I'm having trouble leaning off the mixture. I don't really want everything to come in over 4000rpm so I don't necessarily want massive air flow from big chokes but I wonder if I went up a size if would help me rain in the fuel ratio mix at low and medium revs. Also any thoughts on emulsion tubes. F16 is what I have but there seems to be a school of thought that F11 tubes perform well when mated to a cooking crossflow?
Just for info I'm currently running 30 chokes, 120 mains, 195 air correctors, 45F8 idles jets. I know this is a massive can of worms but it's all part of the fun! Any thoughts/advice from any weber gurus out there?
http://www.burtonpower.com/parts-by-category/ignit...
Pete
x/flow powered sevenish kitcar, 1700cc, BCF2 cam, stage2 head:
weber 40dcoe32
emulsison tube F9
mains 130
air correct. 200
idle 50f9
32 chokes
i recently had this car in my garage..(from a mate)
we tested 2 pair of weber 40dcoe32 both identically jetted:
with first pair the car was running reasonably good
with the 2nd pair it was running like cr*p
idle-jets needed to be changed to 55f9, emuslison tubes to f16 with mains to 125 and air corect. to 180
after those mods the 2nd pair was running similar to the first one
conclusion:
all recommendations from weber, forums, books or wherever only work in theory or by luck.
weber 40dcoe32
emulsison tube F9
mains 130
air correct. 200
idle 50f9
32 chokes
i recently had this car in my garage..(from a mate)
we tested 2 pair of weber 40dcoe32 both identically jetted:
with first pair the car was running reasonably good
with the 2nd pair it was running like cr*p
idle-jets needed to be changed to 55f9, emuslison tubes to f16 with mains to 125 and air corect. to 180
after those mods the 2nd pair was running similar to the first one
conclusion:
all recommendations from weber, forums, books or wherever only work in theory or by luck.
Edited by LLantrisant on Wednesday 3rd September 20:53
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